Mobility limitations are common and costly. Community mobility is an individual?s movement that occurs outside the home and occurs within complex environments. Therefore, the interactions of an individual with the environment must be considered to fully understand how mobility limitations arise. The association of subclinical central nervous system (CNS) abnormalities with mobility in older adults free from neurologic disease is beginning to be established but is typically not studied in relation to environmental challenges. The first aim of this proposal is to characterize the relation between CNS characteristics, peripheral contributors, and community- based environmental challenges in a group of community-dwelling older adults. The second aim will develop and validate lab-based environmental challenges that reflect performance in actual community environments. This proposal incorporates several innovations that will allow me to better assess how the aging brain affects negotiation of real-world environmental challenges: 1) use of community-based environmental challenges in the lab to test community mobility 2) use of wearable, wireless functional near-infrared spectroscopy (fNIRS) for assessment of functional brain changes while participants are walking and 3) a multimodal neuroimaging approach that combines functional measurements from fNIRS with structural imaging. To successfully complete this research, I propose four training aims: 1) Acquire skills in measurement of gait in the lab and the real world; 2) Become an expert in use of near-infrared spectroscopy in mobility research; 3) Acquire advanced skills in in instrument development and testing; and 4) Continue to develop leadership and professional skills. These training aims will help me to achieve my immediate goals of establishing the relation between brain aging and limitations in community mobility as well as my long term goals of better understanding the contributors to community mobility in order to inform future intervention strategies. This research will establish the association between CNS function and negotiation of community-based environmental challenges, will establish the validity of tools for use in future studies, and will provide evidence towards novel intervention strategies to improve community mobility of older adults.